Cladistics

This cladogram shows the assumed evolutionary relationship among various insect groups. In such cladograms, the length of the horizontal lines indicates time elapsed

Cladistics (Greek: κλάδος, klados, "branch") is a classification system for species which seeks to determine how different species are related. Evolutionary cladistics is based on the hypothesis of common descent, or the belief that all life on Earth is related. Creationist cladistics, on the other hand, is based on the hypothesis of created kinds, or the idea that all life on Earth was created by God fully formed and functional, so that some forms of life are related, but others are not.

The term was coined by Ernst Mayr as a reference to the unpleasant emphasis solely on genealogical lineages.[1] One variation of systematics is known as phylogenetic systematics[2] (from the Greek words for phylon (φῦλον, phylon) which means race and genetics (γενετικός, genetikos) which means birth), a system started by the German entomologist Willi Hennig.[1] Instead of relying only upon morphology, cladists also use fossil evidence, genetic, and biochemical analysis to construct treelike diagrams called "cladograms". A cladogram is constructed only from the derived character states shared by pairs of taxa as opposed to the phenogram that is constructed from the total number of character states shared by any pair of taxa.[3]

Contents

Cladistics and Taxonomy

Cladistics is different from taxonomy. Taxonomy, devised by the creationist Carolus Linnaeus, classifies species by their characteristics, but makes no claim to their ancestry. Cladistics, on the other hand, is the study of the ancestry of species. Cladistics advocate classification by pure genealogy without any attention to the concepts of similarity of function or biological role.[4] Due to their assumption of common ancestry, evolutionists sometimes equate cladistics and taxonomy, assuming that because lifeforms are similar, they must be related. Creationists do not equate the two, because they recognize that similarities between species do not necessarily imply common ancestry.

A massive web-based cladistics project with an evolutionary perspective can be found at The Tree of Life[1]. Here a group of biologists from around the world are attempting to put the consensus evolutionary relationships of all organisms onto the web. The creation science community is currently without a similar collaborative resource for the created kinds. However, the Baraminology Study Group has developed some useful databases, such as the HybriDatabase[2], and the Multivariate Analysis Repository[3], which are sure to become valuable tools in our study of the history of created kinds.

Cladogenesis

Cladogenesis is a term used to describe a splitting event within a species hierarchical tree based on their common genetic and morphological makeup. This branching will form a clade, a cluster of lineages,[5] or what is a group of species consisting of an ancestor specie and all of its descendant species.[6] It can be seen in the trademark branching created during the speciation modes of heavy geographical isolation. Another process related to cladogenesis is termed anagenesis, an "upward" movement of the phlyletic lineage without splitting, a gradual change from an ancestral to a derived condition.[7]

Problems that arose

Ironically, since cladistic got preponderance, and similarity became the sole criterion for the inference of relationships, paleontologists have discovered that the most likely candidates for the ancestor of Archaeopteryx lived tens of millions of years later.[8] Another kind of problem in evolutionary cladistics occurs when sometimes a new fossil does not fill a gap, but creates additional gaps on other branches of a cladogram.[9]